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HOME > FEWS-NET > Weekly Weather Summaries
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Weekly Weather Summaries Archive
January 10, 2001
The cold sea surface temperature of La Nina in the eastern Pacific has
continued into the current winter which results in the warm surface
water extended toward Indonesia. This warm surface water is associated
with greater atmospheric convective activity. Therefore, the potential
exists
for above average number of tropical storms in the South Indian Ocean.
Tropical Cyclone Ando was the first named storm of the season and passed
just east of Madagascar. Tropical Cyclone Bindu was last reported near
16S, 72E and we will continue to issue bulletins on position, strength
and forecast as received. As indicated previously, the CPC Homepage
includes a 24-hour infrared animated loop. The web address is:
www.cpc.ncep.noaa.gov/products/fews/24_hour_loop.html
Area of northern Mozambique and Zambia is highlighted for potential
local flooding as described.
The heat over the cornbelt is included because of the POSSIBLE adverse
effect on crops. Once the continental tropical airmass is replaced with
a more maritime airmass (a discontinuous process on the
days-weeks-months timescale), that threat will be over (should be late
Friday). Since this is
a discontinuous process, if there are no indications for such an episode
next week, it will be removed without regard for continuity, an
appropriate action for such a process on the 7-day timescale.
Dryness persisted across much of Kenya and northeastern Uganda. Although
Kenya and northeastern Uganda benefitted from good rains the previous
10-day period, long term dryness has persisted over much of this
sub-region, where only light to moderate rains (1-40 mm; 3-70% of
normal) were observed. Rainfall was also light to moderate across much
of Tanzania. Light rains were also observed over much of Botswana and
northern Namibia.
Because of the long-term dryness in the area of Kenya, we will continue
to watch carefully this situation.
January 18, 2001
Tropical Cyclone Bindu posed no threat to the African continent and has
diminished in strength to the point that coverage has been dropped. A
new Tropical Depression has formed, but is not yet named. We will
continue to issue bulletins as received.
Hot, dry weather continued in northern and central Namibia, though
thunderstorms brought some relief to southern Angola on January 15-16,
with some rain penetrating northern Namibia. Four-week rainfall totals
through January 13 were less than 25% of normal at some locations in
central and northern Namibia.
Unusually warm and dry weather has covered most of southern Africa since
January 2, though thunderstorms brought rains to northern Zimbabwe and
parts of northern South Africa on January 15-16. If the dry pattern
that includes southern Zimbabwe, Botswana, southern Mozambique, and
South Africa's maize triangle continues, it may have an adverse impact
on the maize crops in
the region, as we are now getting into the critical growth stages for
that crop.
Low pressure in the Mozambique Channel is bringing heavy rains to
Madagascar and northern Mozambique.
Though heavy rains have caused flooding in southern Kenya, where 4-week
rainfall has been more than 200% of normal, the long-term drought
persists in northern Kenya. Satellite vegetation data suggests the
dryness extends into southern Somalia.
January 25, 2001
Tropical Cyclone Charly is passing well to the east of the African
continent and is diminishing in strength. A Tropical Depression formed
just to the east of Madagascar, but this storm has moved over land and
did not become cyclone strength. It has added, however, to the large
rainfall totals received this year over Madagascar, over 400 mm since
January 11 in some locations. The NWS extended model suggests that this
storm may re-intensify over the warm water of the Mozambique channel.
We will continue to monitor the situation and issue bulletins as
necessary. Cyclone bulletins will be transmitted as received.
In southern Africa, rainfall remained generally below normal over most
areas. Scattered showers brought some dryness relief to southern Angola
and northern and central Namibia, but cumulative rainfall for the season
has remained well below normal. Dry conditions continued to prevail over
southern Namibia and southern Botswana. Light to moderate rains fell in
southern Mozambique, much of Zimbabwe and northeastern South Africa..
Torrential rains struck large areas of Madagascar, as a tropical low
pressure area remained nearly stationary over the Mozambique Channel.
Totals of 150 to 400 mm were common over all but the far northern and
southern areas of the island, with up to 476 mm inundating the Besalampy
area on the northwest coast. Heavy rains also fell over northern and
eastern Zambia and into southern DRC, southern Malawi and northern
Mozambique. Unseasonably heavy rains fell over southern and western
coastal areas of South Africa. Temperatures were generally 1 to 2
degrees C below normal over southern Africa except 2 to 3 degrees above
average in northern Namibia and northeast South Africa.
In East Africa, above-normal rains covered much of Tanzania, parts of
southern Uganda and southwestern Kenya. Temperatures were near average
across the region.
In central Africa, unseasonably heavy rains fell in western DRC and
southern Congo. Temperatures generally averaged 1 to 2 degrees C below
normal across the region except in Gabon, where they were 1 to 3 degrees
C above average.
In West Africa, the dry season continued over the Sahel and the Gulf of
Guinea region. Temperatures were 1 to 3 degrees C above average except
in Chad, where they averaged 1 to 3 degrees C below normal.
January 31, 2001
Please note that we have changed the area of the accompanying map to
include all of Africa and Madagascar. To do this we have had to then
separate the graphic from the text. They are now in two files, a and b.
Tropical Cyclone Charly passed well to the east of the African
continent and posed no threat to the continent. A Tropical Depression
formed just to the east of Madagascar, but this storm moved over land
and did not become cyclone strength. It has added, however, to the
large rainfall totals received this year over Madagascar.
We continue to monitor the sea surface temperature over the Pacific
Ocean to determine the continuing extent and magnitude of the La Nina
situation as it pertains to the likelihood of development of cyclones
in the Indian Ocean along with their steering currents. Cyclone
bulletins will be transmitted as received.
Very heavy rains struck central and northern Mozambique in the past week
and continued to plague parts of Madagascar. The area in Mozambique
bearing the brunt of the torrential rains extended from near Beira in
Sofala province northward along the coast to Quelimane in Zambezia
province. Satellite-estimated rainfall for the 7 days through January
29 exceeded 300 mm (12 inches) in this zone, with some amounts locally
exceeding 500 mm (20 inches). The area of heavy rains included the
lower reaches of the Zambezi River. Heavy rains have fallen throughout
northern Mozambique, with estimated weekly amounts reaching 500 mm
locally in Cabo Delgado in the northeast. Beira along the central coast
reported a one-day total of 106 mm on January 28 on top of 27 mm the day
before. Satellite imagery indicated that heavy thunderstorms struck
this area again on the 30th. In Madagascar, 7-day rainfalls exceeded
300 mm and ranged up to 500 mm in west-central areas and along the
northwest coast. Locally heavy rains have also fallen in northeastern
parts of the island.
Heavy rains extended northward into Tanzania, southwestern Kenya, and
Malawi, with 200 mm (8 inches) common in Malawi and southern Tanzania.
Wet conditions expanded westward across Zambia into Angola, as locally
heavy rains hit interior portions of northwestern and southwestern
Angola--areas that had previously been abnormally dry.
Daily showers since January 18 have benefitted the dry areas in central
and northern Namibia, but very dry conditions have developed across
Botswana, central and southern Zimbabwe, southern Mozambique, northern
South Africa, and Swaziland. Rainfall has been light and sporadic in
this region since January 2, and periods of high temperatures have
aggravated the dryness. The lack of moisture coincides with the
critical growth stage for maize crops in the region.
February 8, 2001
The circulation pattern appears to remain in a strong La Nina mode with
neutral conditions not forecast to occur until this coming spring
season. We continue to monitor the sea surface temperature over the
Pacific Ocean to determine the continuing extent and magnitude of the
La Nina situation as it pertains to the likelihood of development of
cyclones in the Indian Ocean along with their steering currents.
Cyclone bulletins will be transmitted as received.
On a shorter time-scale we note that the numerical forecast models
indicate a continued threat of severe localized rainfall through the
coming weekend.
As forecast last week, very heavy rains struck central Mozambique during
February 4-6, increasing the potential for additional flooding. The rains
hit some of the areas affected by heavy rains in late January, but also
struck farther south, including areas that had been enduring drought.
The heaviest rains fell on February 4-5, with satellite-estimated 24-hour
amounts exceeding 100 mm from central Inhambane province in the south to
central Zambezia province in north-central Mozambique. Heavy rains also
extended westward into extreme southeastern Zimbabwe. In Mozambique,
estimated totals locally exceeded 200 mm in northern Inhambane and southern
Sofala. On the preceding day, thunderstorms dropped 50 mm or more over
large areas of central Mozambique as well as northeast Zimbabwe. As a
result, some locations in south-central Mozambique may have received as
much as 300 mm of rain in 2 days. Satellite imagery on the 6th indicated
that heavy showers again fell over the same area, further adding to the
rainfall totals. Elsewhere, heavy rains diminished across Madagascar,
Tanzania and southern Kenya, but excessive rains also struck southern
Malawi near the border with Mozambique. Drought continued over extreme
southern Mozambique, with only light rains falling over most of Gaza
province so far this month, continuing the dry trend from January. The
recent deluge ended drought across much of Inhambane province just to the
north. Abnormally dry conditions persisted over south-central and
southwestern Zimbabwe, as well as northern South Africa and much of
Botswana.
February 14, 2001
We continue to monitor the sea surface temperature over the Pacific
Ocean to determine the continuing extent and magnitude of the La Nina
situation. Cyclone bulletins will be transmitted as received.
On a shorter time-scale we note that the numerical forecast models
indicate a continued threat of severe localized rainfall.
Heavy rains continued over parts of central Mozambique following the
February 4-6 deluge, though amounts were not as extreme. According to
satellite rainfall estimates, the provinces of Tete, Sofala, and
Zambezia have sustained the brunt of the rains since the 6th, with the
heaviest rains (over 75 mm) falling on Tete province on February 6-7.
Weekly rainfall totals through February 11 exceeded 150 mm across much
of central Mozambique, with estimated isolated totals of 250 mm over
southern Sofala. Excessive rains (over 150 mm) also fell over extreme
southeastern Zimbabwe, extreme southern Malawi, south-central Angola,
and scattered locations in southern and western Zambia. Rains
diminished in Tanzania, Kenya, and Madagascar. Abnormal dryness
persisted in Namibia, central and southern Botswana, extreme southern
Mozambique, Swaziland, and much of South Africa. Four-week rainfall
totals are generally under 50% of normal across this region. The recent
heavy rains have nearly eliminated dryness from Zimbabwe, with only the
extreme south remaining abnormally dry. To the north, the first season
(belg) rains appear to have started on schedule in Ethiopia. Last year,
these rains virtually failed.
February 22, 2001
We continue to monitor the sea surface temperature over the Pacific Ocean
to determine the continuing extent and magnitude of the La nina situation.
The atmospheric circulation remains in a La Nina state with the forecast
models suggesting a possible weakening to a neutral state this Spring.
Thus, for the next month we anticipate a possible continuation of the
current situation with greater than normal precipitation in the region of
Mozambique. On a shorter time-scale we note that the numerical forecast
models indicate a continued threat of severe localized rainfall. Cyclone
bulletins will be transmitted as received.
Additional heavy rains fell in Mozambique's Zambezia Province during
February 13-19, with satellite estimates exceeding 150 mm over interior
areas adjacent to the Malawi border. Similar heavy amounts also
accumulated over parts of southern Malawi. Heavy rains fell again in
other parts of central Mozambique, with totals exceeding 100 mm in coastal
Sofala province and in extreme northeastern inhambane in the south.
Satellite estimated rainfall reaching 150 mm in Tete Province added to the
excessive rainfall totals affecting Mozambique's Zambezi River Basin.
Moderate to heavy rains relieved dryness across extreme southern Mozambique
in Gaza and Maputo. Elsewhere in southern Africa, increased rainfall
benefited dry areas across Namibia, Botswana, South Africa, and southern
Zimbabwe. In particular, heavy showers (25-75 mm) alleviated dryness in
extreme northern South Africa and adjacent Zimbabwe on February 20. Despite
some recent rainfall, abnormally dry conditions have persisted since the
start of the year in much of Botswana, northeastern Namibia, and part of
South Africa's maize triangle.
February 28, 2001
The Pacific Ocean sea surface temperature remains in a relatively weak
La Nina situation and the forecast models suggest a possible weakening to
a neutral state this April. Although the tropical cyclone threat has been
very low over the past several weeks, we continue to monitor the situation
and bulletins will be transmitted as received.
Heavy rains tapered off during the past week in the flood-affected areas
of Mozambique, with estimated amounts during February 20-26 mainly in the
10 to 75-mm range. This contrasts with the 75 to 200 mm that accumulated
during the preceding week. Rainfall also dropped off in Malawi, Zambia,
and Zimbabwe. Nevertheless, estimated rainfall amounts locally topped 75 mm
in Mozambique's Tete and Zambezia provinces, as well as in south-central
Zambia and west-central Zimbabwe. Satellite imagery on February 27 shows the
return of heavy thunderstorms to southern Malawi and adjacent portions of
Mozambique's Zambezia province. In the areas that had been earlier abnormally
dry, increased rainfall continued to add to soil moisture, with amounts of 10
to 75 mm across much of Namibia, Botswana, and the summer crop areas of South
Africa. In East Africa, long-term drought continued across Kenya's pastoral
areas and adjacent portions of Ethiopia, Uganda and Sudan.
March 8, 2001
The Pacific Ocean sea surface temperature remains in a La Nina situation and
the forecast models suggest a possible weakening to a neutral state this
May-June. A tropical depression has formed over the northern Mozambique
Channel and is currently moving south-southwest. This disturbance may
intensify in the next 48 hours and poses a threat to eastern Mozambique and
western Madagascar. We continue to monitor the situation and bulletins
will be transmitted as received.
A tropical disturbance in the Mozambique Channel was bringing heavy
thunderstorms to northeast Mozambique and the Comoro Islands on March 6-7,
according to satellite imagery and the latest rainfall reports. Six-hour
rainfall totals on March 7 totaled as high as 91 mm in the Comoros. On
March 8, the disturbance was located just off the coast of the Nampula
Province in Madagascar, based on the latest report from the Joint Typhoon
Warning Center. Potential for development was rated as good. The heaviest
rains so far have been mainly north of the ares in Mozambique affected by
the January-February rainfall and flooding. The current rains have been
striking the provinces of Cabo Delgado and Nampula.
For the week ending March 5, totals were seasonably heavy across Mozambique,
although satellite estimates indicated that locally heavy amounts (75-100mm)
continued over the central provinces, including Sofala, Manica, Tete, and
interior Zambezia. Locally heavy rains also persisted over southern Malawi
and central and western Zambia. Widespread rains of 75-125 mm covered central
and northern Zimbabwe.
March 15, 2001
It is likely that cold episode Pacific sea surface conditions will gradually
weaken over the next several months, with near-normal conditions likely
during the summer of 2001. This assessment is generally supported by the most
recent NCEP statistical and coupled model forecasts, as well as by other
available coupled model and statistical model predictions, which indicate a
gradual weakening of cold episode conditions during the next few months.
Thereafter, the models indicate near-normal or slightly warmer-than-normal
conditions during the second half of 2001.
Tropical Cyclone Dera affected the Mozambique Channel, western Madagascar,
and eastern Mozambique from March 7-12. Intensifying to cyclone strength as
it approached the center of the channel, Dera spared most flood ravaged areas
of Mozambique, but did produce heavy rains over the northeast provinces and
southwestern Madagascar. 24 hour precipitation totals on March 8th approached
100 mm in the provinces of Niassa, Cabo Delgado, Nampula, and northern
Zambezia of Mozambique. Up to 50 mm of rain fell over southwest Madagascar
on March 10 as the cyclone exited the region.
Weekly rainfall totals from March 6-12 locally exceeded 150 mm in northeast
Mozambique and exceeded 100 mm in southwestern areas of Madagascar. The
winter crop belt region of Morocco received some relief, with locally 15 mm
weekly precipitation totals. The drought affected area of southern
Ethiopia received regional precipitation amounts exceeding 50 mm, but northern
Kenya remains quite dry. As expected, rainfall has begun in southern areas
of west Africa, with weekly totals exceeding 50 mm in parts of Cote d'Ivoire
and Ghana.
March 21, 2001
Since early February 2001, SSTs have become anomalously warm in many sections
of the eastern tropical Pacific with a gradual expansion of the area of
positive equatorial subsurface temperature anomalies into the central Pacific.
This evolution is consistent with a slow decay of the subsurface thermal
structure that characterizes the mature phase of cold episodes. Thus, it is
likely that cold episode conditions will gradually weaken over the next several
months, with near-normal conditions likely during the summer of 2001. This
assessment is generally supported by the most recent NCEP statistical and
coupled model forecasts, as well as by other available coupled model and
statistical model predictions, which indicate a gradual weakening of cold
episode conditions during the next few months. Thereafter, the models indicate
near-normal or slightly warmer-than-normal conditions during the second half
of 2001.
Areas hit by heavy rains in northeastern Mozambique during the preceding week
recorded lighter amounts during the week ending March 19, with totals mostly
under 50 mm. However, rainfall tended to remain above normal from Mozambique
to Zambia, with locally heavy rains exceeding 75 mm in Tete province in
northwest Mozambique and various locations in the south. Estimated totals
exceeded 150 mm along the southern coast of Mozambique's Inhambane province.
Amounts also exceeded 75 mm in extreme southern Malawi and in isolated
locations in northern and eastern Zimbabwe and central Zambia. Northern
Tanzania continued quite dry, while long-term drought persisted in northern
Kenya. Short-term dryness has developed to the south. Four-week rainfall
totals are under 50% of normal in central and southern Kenya, where the main
rainy season is normally progressing. Seasonal rains fell over central,
northern, and western Ethiopia. The seasonal rains in West Africa continued
to slowly advance northward along the Gulf of Guinea coast, but amounts
remained below normal in southern parts of Togo, Benin, and Nigeria. There
was little or no rain in Morocco, where chronic dryness has affected southern
wheat areas this season. Below-normal rain also prevailed in Algeria and
Tunisia, with rainfall generally less than one-half normal in the past 4 weeks.
High temperatures worsened the dryness in northern Africa.
March 29, 2001
An area of storminess has been noted at about 10S, 80E. While this area
has been posted as having a poor chance to magnify into an actual
cyclone, the NWS forecast models are forecasting it to migrate westward
toward northern Madagascar and Mozambique. The potential exists for
significant rainfall from this system during the early part of next
week. We will maintain watch on this system as it moves and develops,
providing bulletins as necessary.
Rains continued to diminish in central Mozambique, including the
flood-affected Zambezi River basin, with weekly rainfall totals through
March 26 generally under 50 mm. Most of southern Mozambique recorded
less than 10 mm of rain. Isolated rainfall totals did exceed 75 mm
locally along the central Mozambique coast in northern Sofala and
southern Zambezia. Beneficially drier weather, with rainfall amounts
mostly under 50 mm, also covered southern Malawi, southern Zambia, and
most of Zimbabwe. In East Africa, rainfall increased, easing short and
long-term dry conditions in Kenya and southern Ethiopia. Much more rain
is needed to end the severe long-term rainfall deficits over pastoral
areas of Kenya, but the rainy season appears to be starting on
schedule. Showers also helped to ease short-term dryness in Tanzania,
Rwanda, and Burundi. In West Africa, unusually warm and dry weather
persisted over Togo, Benin, and Nigeria, although scattered
thunderstorms brought some relief to coastal Nigeria. Abnormally warm,
dry weather continued over Morocco, Algeria, and Tunisia, as rainfall
remained scanty. Amounts have totaled under 25% of normal in the past 4
weeks in southern Morocco, northeastern Algeria, and northern Tunisia.
Beginning in early April we will reinitiate coverage of the
Intertropical Convergence Zone as it migrates northward and compare it
against its climatological position. This information will be posted
within our USAID/FEWS web site.
April 4, 2001
A path of storminess continues on a path at about 11S. While the areas
of depression have not been forecast to magnify into an actual cyclone
they constitute a considerable threat of significant rainfall to the
areas of Madagascar and Mozambique. We will maintain watch on these
systems as they progress, providing bulletins as necessary.
Rains further diminished across flood-affected areas of southeastern
Africa, with amounts during the week ending April 2 mostly under 10 mm
in Zimbabwe, central Mozambique, southern Malawi, and southern Zambia.
Heavy rains eased long-term and short-term dryness in southern Ethiopia
and central and western Kenya, as isolated amounts exceeded 75 mm in the
core of the drought area in northern Kenya. In contrast, much of Rwanda
and Burundi may have missed the recent heavy showers affecting other
parts of the region, according to satellite estimates, with amounts
under 25 mm in parts of both countries. The rainy season appears to
have begun poorly in Rwanda and Burundi, particularly in Burundi. In
West Africa, showers increased over Ghana, Togo, Benin and Nigeria, as
amounts exceeded 75 mm locally during the past week, but more rain is
needed to overcome the deficits built up during March. Abnormally warm,
dry weather continued over Morocco, Algeria, and Tunisia, as rainfall
was light to nonexistent. No measurable rain fell during the entire
month of March at a number of locations in Algeria's crop region.
Amounts from all three countries generally totaled 0 to 25% of normal in
March. Heat aggravated dryness, as monthly temperatures averaged 3 to 5
degrees C above normal.
April 11, 2001
We continue to maintain watch on the evolution of the Pacific La Nina
situation. Currently, relatively warm surface water has been observed over
the eastern tropical Pacific ocean. However, the subsurface warm water
remains to the west and has shown little indication that it will soon migrate
to the east. Thus, we linger within a transition period with conversion to an
El Nino state perhaps some months away.
Abnormally dry weather spread across northern and eastern Ethiopia and much of
Somalia during the past week. The first season (belg) rains have been erratic
over Ethiopia this season, with below-normal rains over eastern agricultural
areas and normal to above normal in the west. Because of little rain in the
past 2 weeks, dryness has increased in the east and is developing in the north.
In Somalia, the main rainy season has been slow to start, with showers limited
to the far south. The median start of the rainy season is the first week of
April. In contrast, the rainy season is in full swing over Kenya, contributing
to long-term drought relief in the pastoral areas. Satellite-estimated rainfall
totals improved over Rwanda and Burundi, but the season has been abnormally dry
over northeastern and central Tanzania. Abnormally wet conditions have
developed across large areas of central and southwestern Africa, as heavy
showers dropped over 75 mm of rain locally in Angola, Namibia, Congo, and DRC
during the week ending April 9, according to satellite estimates. Estimated
totals exceeded 150 mm in parts of western Angola and even in isolated parts of
northern Namibia. Rainfall continued to diminish across the areas of
southeastern Africa affected by flooding, as amounts in Zambia, Malawi, Zimbabwe,
and Mozambique generally totaled 10 mm or less. Scattered thunderstorms
continued along the coast of the Gulf of Guinea, but abnormal dryness persisted
over interior parts of Togo and Benin and as well as northern Ghana and western
Nigeria. In North Africa, drought worsened across Morocco, Algeria, and central
Tunisia, as warm and dry weather continued. Significant rains were limited to
northern Tunisia.
April 19, 2001
Another week of little or no precipitation worsened drought affected
areas of Morocco, northern Algeria, and central Tunisia, with the
Climate Prediction Center rainfall estimates recording precipitation
only in extreme northeast Algeria and northern Tunisia. Weekly totals
were generally less than 25 mm in the aforementioned areas. Monsoonal
rains continued in the Gulf of Guinea with light rains advancing into
the interior parts of the Gulf of Guinea. Parts of Cote D'Ivoire
received an excess of 125 mm for the period from April 10-16. On April
15, after an intense rain-producing storm, as much as 75 mm rainfall was
recorded in west-central areas of the country. While southern Nigeria
continued to receive rainfall amounts exceeding 100 mm in some areas,
most of Togo and Benin, as well as northwestern Nigeria remained quite
dry with barely 10 mm reported for the week. Heavy rains continued in
central South Africa, Angola, DRC, and Cameroon with local rainfall
estimates exceeding 150 mm. However precipitation lessened somewhat in
regions of Central Africa Republic and Congo. Flood-affected regions of
Mozambique, Zimbabwe, Zambia, and Malawi continued to recover as
generally little precipitation fell in the areas. This coincides well
with the ITCZ's climatological jump north in early April and the ending
of the monsoon in southeastern Africa. Much of eastern Africa remains
dry through this period, although some areas have seen recent relief.
Southern Somalia and southwestern Ethiopia received as much as 100 mm
the past week, bringing a little relief to the areas, but most of their
northern regions saw less than 10 mm. The northern half of Tanzania, as
well as Uganda continued to receive good rainfall amounts exceeding 50
mm in most areas, but south-central Tanzania, Burundi, and Rwanda picked
up generally less than 30 mm.
April 25, 2001
Since early February 2001, sea surface temperature's (SST) have become
anomalously warm in many sections of the eastern tropical Pacific, while
remaining below normal in the central equatorial Pacific. Positive SST
anomalies were also observed in the eastern equatorial Pacific during
March-April 1999 and 2000. In both of those years the anomalous warming
of the eastern equatorial Pacific SSTs lasted until late April or early
May and then rapidly disappeared as cross-equatorial flow from the
Southern Hemisphere into the Northern Hemisphere became established and
seasonal rainfall began to increase over Central America, southern
Mexico and the southeastern tropical North Pacific.
Over the past two years there has been a gradual expansion of the area
of positive equatorial subsurface temperature anomalies into the central
Pacific. This evolution is consistent with a slow decay of the
subsurface thermal structure that characterizes the mature phase of cold
episodes. Thus, it is likely that cold episode conditions will gradually
weaken over the next several months, with near-normal conditions likely
during the summer of 2001. Thereafter, the models indicate near-normal
or slightly warmer-than-normal conditions during the second half of
2001. This has implications for the June-August climate in western
Africa and we will continue to monitor the situation.
Heavy showers spread across much of East Africa, easing long-term
drought in Kenya and parts of Ethiopia. However, rainfall amounts
remained below normal in northern Ethiopia from Addis northward, an area
that has seen little rain since late March, according to satellite
estimates and scattered observations. Satellite imagery for April 22-23
suggests a sharp increase in shower activity over eastern Ethiopia,
including the Somali region, an area that has been abnormally dry. A
few showers even penetrated northern Somalia (Somaliland). Heavy rains
across southern Somalia may have been locally excessive, with weekly
estimated amounts over 100 mm. In contrast, unfavorably drier weather
returned to the Burundi-Rwanda area, with weekly amounts well under 25
mm. Showers continued to ease dryness over the interior of the Gulf of
Guinea countries, although an area of dryness persisted from
northeastern Ghana through northern Togo and northern Benin into
northwestern Nigeria. Light to moderate rains during April 20-22
brought slight drought relief to North Africa, especially coastal areas
of Algeria and Tunisia. In southern Africa, unseasonably heavy rains
fell in much of South Africa, southwestern Botswana, central and
southern Namibia and pockets along the eastern coast of Madagascar.
Amounts continued to diminish in the flood-affected areas of
southeastern Africa, as little or no rain fell in central Mozambique,
Malawi, southern and western Zambia and much of Zimbabwe. The drier
pattern coincides well with the slow movement of the ITCZ to the north
of southern Africa. Note from the CPC Website that the ITCZ appears to
be slightly north of the climatological position in the west and south
in the east.
May 2, 2001
Following a 3-week dry spell, seasonal rains resumed in northern Ethiopia,
where rainfall exceeded 25 mm locally. Light rain continued to relieve
dryness in eastern Ethiopia, while satellite estimated rainfall diminished
in southern Somalia, where amounts had been locally heavy during the previous
week. Seasonal rains continued to offer spotty long-term drought relief in
northern Kenya and southern Ethiopia. Satellite data indicated that
unseasonably dry weather covered Rwanda, Burundi and northern Tanzania for
the second week. Unseasonably wet weather covered large areas of southwestern
and west-central Africa from the Congo to South Africa, with especially heavy
rains extending from Namibia southward to central South Africa on April 30-
May 1. Rainfall amounts exceeding 40 mm in 24 hours over Namibia and near
the extreme western portions of South Africa's summer crop areas would be
unusual at the height of the rainy season, but are expecially unusual in late
April-early May. Near-record rainfall amounts for this time of year have
covered Namibia and western and central parts of Botswana and South Africa
during the past 4 weeks. In West Africa, locally moderate to heavy showers
eased dryness during the past week in northern areas of Ghana, Togo, Benin
and Nigeria, but cumulative rainfall totals for the past 4 weeks continue to
be less than one-half normal over parts of this area and over southern Burkina
Faso. In North Africa, rains brought some drought relief to the region, with
up to 25 mm falling in the past week over Algeria. Rainfall was lighter in
Tunisia and Morocco, with negligible rain falling over Morocco's southern
crop areas, where the drought is most intense.
May 9, 2001
The slow evolution of the La Nina event continues and it is likely that
near-normal conditions will exist during the summer of 2001. Thereafter,
the models indicate near-normal or slightly warmer-than-normal
conditions during the second half of 2001. This has implications for the
June-August climate in western Africa and we will continue to monitor
the situation.
Locally heavy showers further eased dryness in northern Ethiopia and
northern Somalia during the first week in May, but drier weather spread
across southeastern Ethiopia and much of Kenya, and little rain fell
over central and eastern Tanzania. Parts of northern, eastern, and
southern Kenya have recorded negligible rain for 3 weeks. Four-week
cumulative rainfall has been near or under 50% of normal in these areas,
and similar dryness has affected parts of eastern Ethiopia and northern
and central Tanzania. Rainfall increased in the Rwanda, Burundi,
northwestern Tanzania region, easing dry conditions. In southwestern
Africa, rainfall diminished in areas recently hit by excessive rains,
although unseasonably heavy rains did hit parts of eastern Namibia,
southern Botswana, and western South Africa once again in the past
week. To the north, the rainy season has been slow to start in southern
Chad, northern Central African Republic, and south-central Sudan.
Rainfall has been negligible in this region during the past 3 weeks, and
high temperatures have further increased dry conditions. Additional
light to moderate rains fell over North Africa from northern Morocco to
Tunisia, but the moisture comes too late in the season to have a
significant impact on the drought. The rains missed most of southern
Morocco, where the drought is most severe.
May 16, 2001
As indicated in previous weeks, it is likely that near-normal sea
surface temperature conditions will exist in the Pacific during the
summer of 2001. Thereafter, the models indicate near-normal or slightly
warmer-than-normal conditions during the second half of 2001. We are
currently computing the July-August-September forecast for the Sahel and
the forecast will be available next week. We note also that the
international climate forum will be held next week with the resultant
consensus forecast.
Dry conditions intensified during the past week over much of Kenya,
southern Ethiopia, interior southwestern Somalia, northern Tanzania,
Rwanda and Burundi, as this area recorded little or no rainfall. For
eastern Kenya and adjacent parts of Ethiopia and southwestern Somalia,
this was the second week of dry weather. Elsewhere, seasonably dry
weather prevailed across southwestern Africa from Angola to South Africa
following persistent wetness since late March. To the north, increased
showers (1-25 mm, locally heavier) dampened dry soils from southern Chad
through northern Central African Republic to south-central Sudan. This
area had seen virtually no rain in the prior 2 weeks. In West Africa,
the rainy season continued weak in southwestern Burkina Faso, with
rainfall amounts mostly under 25 mm. Over North Africa, moderate to
locally heavy rains further eased dryness in northern Tunisia, but
lighter amounts fell in Algeria, and little or no rain fell in Morocco.
May 23, 2001
Guidance for the Sahel Rainfall in Jul-Aug-Sep 2001 At One Month Lead
The Sahel, defined here as the region between 10-25 N and 18 W-45 E,
receives the bulk of its annual mean rainfall during the northern
hemisphere summer when the ITCZ reaches its northernmost position. For
our forecast method, quasi-global SSTs between 40 S and 60 N at a
resolution of 10 by 10 lat-lon are used to predict the Sahel rainfall.
The diagnostic data produced by the statistical analysis indicate that
the current weak cold episode of ENSO does not have much impact on the
forecast for Jul-Aug-Sep Sahel rainfall at one month lead. However,
cold SSTs over the equatorial central Pacific tend to be associated with
above normal rainfall over the Sahel. NCEP statistical and coupled
model forecasts, as well as other available coupled model and
statistical model predictions, indicate a gradual weakening of cold
episode conditions during the next few months. Another factor
modulating rainfall over the Sahel is Atlantic SSTs. Over the past
year, near-to-above-normal SSTs prevailed across much of the Atlantic.
Consistent with the weak global SST anomalies, the current forecast does
not have much skill in the prediction of Jul-Sep 2001 Sahel rainfall and
calls for climatology in many parts of the region. However, slightly
higher than climatological probabilities for above normal rainfall are
expected over western Senegal, southwestern Mauritania, central Mali,
and eastern Chad, while slightly higher than climatological
probabilities for below normal rainfall are expected over parts of
central Sahel.
During the past week, little or no rain fell over eastern and southern
Ethiopia, as well as much of Somalia and Kenya, increasing the risk that
the rainy season may be coming to an early end. This would especially
be a concern for eastern Ethiopia, where the rainy season began several
weeks late. The season may also be ending early in Rwanda, Burundi, and
northwestern Tanzania, as rainfall amounts were light in this region.
Increased rainfall improved dry conditions in south-central Sudan and
northern Central African Republic, but rainfall deficits persisted.
Weekly amounts of 1 to 25 mm did little to improve rainfall deficits in
southeastern Chad, but greater amounts fell in the southwest. Moderate
to heavy showers eased dryness in western Burkina Faso, as lighter rains
fell from southern Mali into Guinea. The rainy season has been somewhat
slow to start in this region. Rainfall has also diminished over
interior portions of Cote d'Ivoire, Ghana, Togo, and Benin, with much of
this area recording 4-week accumulations under 50% of normal. In
contrast, locally heavy rains left as much as 200 mm along the coast of
Cote d'Ivoire. This pattern is in agreement with the observed location
of the ITCZ being a bit south of the normal position in the east and
near normal in the west.
May 30, 2001
During the past week, little precipitation fell once again through much
of eastern and southern Ethiopia, while western parts of the country
received amounts exceeding 150 mm. Rainfall was sparse throughout most
of Somalia, as only northern areas accumulated more than 20 mm. Dry
conditions continued in most of Kenya and Tanzania, and light showers
continued in eastern coastal areas of Madagascar. It appears that the
rains are diminishing on schedule in these areas of eastern Africa.
Widespread rains fell throughout southern Sudan, with common values
exceeding 30 mm, and amounts estimated up to 100 mm. These rains
extended into all of eastern CAR, but did not continue through southern
Chad as generally less than 15 mm fell. The ITCZ in this area does
continue to be more southward than the climatological mean, but movement
has generally been northward the past few weeks as expected. See
http://www.cpc.ncep.noaa.gov/products/african_desk/ITCZ/ITCZ.html for
further information. Healthy rainfall amounts fell throughout interior
portions of sub-sahelean Africa, with amounts exceeding 75 mm somewhat
common. The region around Sierra Leone has been slightly dry the past
month, and precipitation amounts less than 30 mm for the week ending May
28 are representative of the season so far.
June 6, 2001
For the last assessment we discussed the outlook for West Africa region
based on the CPC Africa Desk long-lead forecast. Included with this
assessment is a sahel.pdf file of the consensus forecast developed at
the West Africa Climate Forum. As indicated from our previous
discussion, the area forecast is generally for climatology reflecting
the transition state of the sea surface temperatures. The exception is
in Zone III from Liberia to southwest Nigeria where an above normal
precipitation is forecast.
The rainy season has ended somewhat early across the African Horn.
Little or no rain fell during the past week in the Somali region of
southeastern Ethiopia as well as most of Somalia and Kenya. Only
western and coastal areas of Kenya picked up significant rains.
Preliminary estimated rainfall for the season from February through May
indicate cumulative rainfall may have been well under 50% of normal in
southeastern Ethiopia, with some locations under 25% of normal.
Cumulative rainfall was generally 50 to 80% of normal across Somalia,
Kenya, Tanzania, Rwanda and Burundi. In the Sahel, scattered
thunderstorms fell over southern Chad, but conditions appear to remain
drier than normal, and the dryness appears to extend into extreme
northern Cameroon and parts of northeastern Nigeria, although showers
brought locally heavy rains to northern Nigeria. Scattered
thunderstorms improved moisture conditions in Burkina Faso, southern
Mali and Guinea. The rains have been slow to advance northward into
Guinea-Bissau and southern Senegal, but this is too early in the season
to be a problem.
June 13, 2001
As depicted in the Climate Prediction Center website at
www.cpc.ncep.noaa.gov the Intertropical Convergence Zone in the area
of 10-20E remains several degrees latitude south of its climatological
position impacting the timing of the seasonal rains in the area.
In East Africa, dry weather prevailed from Somalia and eastern Ethiopia
southward through eastern Kenya into Tanzania. There is little prospect
for significant dryness relief until the second rainy season begins in
October. To the west, satellite rainfall estimates as well as
vegetation indices continued to point to a slow start to the rainy
season in southeastern Chad, extreme northern CAR, and adjacent portions
of Sudan. The heaviest rains of the season, with weekly totals mostly
over 40 mm, relieved dryness in the western half of southern Chad.
Rainfall remained light in southern Niger and adjacent parts of
northeastern Nigeria, with weekly amounts mostly under 5 mm. It is,
however, still early in the season, and cumulative rainfall for the
rainy season could easily be normal if the rains start soon. Some
pockets of below-normal rainfall persisted in Burkina Faso, but rainfall
has been ample in the southeast. Locally excessive rainfall continued
in central and southern Nigeria, with satellite estimates exceeding 75
mm on June 10.
June 20, 2001
The seasonal rains advanced northward into Niger during the past week,
improving moisture conditions in northern Nigeria and southern Niger.
In contrast, satellite-estimated rainfall diminished in parts of
southern Chad and remained light in adjacent west-central Sudan,
resulting in continued below-normal moisture conditions, especially from
southeastern Chad into Sudan. Locally excessive rains exceeding 100 mm
fell in southern Sudan and western Ethiopia. Heavy showers continued in
eastern Burkina Faso, but some dry pockets persisted in other areas,
especially near the border with Ghana, according to satellite estimates
and ground stations.
June 27, 2001
While the position of the ITCZ has been south of its normal latitude
over the previous weeks, during the second dekad of June, the ITCZ
advanced north in the mid-section of the continent to its more normal
position. The latest maps of the ITCZ location can be viewed on the
Climate Prediction Center Homepage at:
http://www.cpc.ncep.noaa.gov/products/african_desk/ITCZ/ITCZ.html
For the period from June 19-25, 2001, rainfall was generally seasonal
over most of the African continent with the exception of unusually heavy
rains in parts of southern Africa. Parts of eastern Botswana and
central South Africa received up to 35 mm total precipitation, while
widespread amounts greater than 10 mm were estimated. Tropical Cyclone
21s formed on June 21 in the southern Mozambique Channel with maximum
sustained winds of 45 kts, but weakened by the 23rd without making
landfall. In eastern Africa, heavy rains once again fell in coastal
areas of Kenya and northern Tanzania, with amounts exceeding 100 mm
locally. Little or no rain fell in Somalia and eastern Ethiopia, but
western Ethiopia accumulated scattered amounts of 75 mm, with a large
region of 30 mm or greater totals. Seasonally heavy rains totaling
greater than 100-200 mm fell again in coastal Cameroon and eastern
Nigeria, and local totals exceeding 100 mm were estimated in areas of
Ghana, Togo, and northern Nigeria. Generally, the monsoonal rainfall
pattern coincides well with the latest plotted ITCZ position.
July 4, 2001
Current sea surface temperature data indicate that it is likely that
near-normal sea surface temperature conditions will continue to exist in
the Pacific during the summer of 2001. Thereafter, the models indicate
near-normal or slightly warmer-than-normal conditions during the second
half of 2001.
The seasonal rains continue to advance northward on schedule over most
of the Sahel, although rains remained slow to move into central Senegal.
Generally, both the Sahel and Gulf countries recorded moderate showers,
while light to moderate rain fell over central and eastern Africa.
Unseasonable rains fell in South Africa.
July 11, 2001
The seasonal rains continued favorable across most of the Sahel,
although rainfall remained somewhat below normal in parts of Senegal and
Gambia. Amounts tapered off significantly over the Gulf of Guinea
countries, as the mid-season dry period appeared to take hold. Locally
excessive rains exceeding 75 mm fell in western Mali, northeastern
Burkina Faso, central and northern Cameroon, and southern Chad.
Beneficially drier weather prevailed in areas to the south earlier hit
by heavy rains, including Ghana, Nigeria, and southwest Cameroon. In
Sudan, the seasonal rains have been slow to become established in
northern agricultural areas in the central and western parts of the
country.
July 18, 2001
During July 1-10, 2001, the West African portion of the ITCZ remained
stationary at 17.4 degrees N, which is close to the long-term mean of
17.5 N. Overall progress so far this season has been typical despite the
failure of the ITCZ to advance northward during this period. In
contrast, the ITCZ remained south of normal across eastern Africa (20-35
degrees E), its mean position of 14.2 N a full degree south of its
long-term mean position. The convergence zone has been consistently
south of normal during this season. The ITCZ was near its normal
latitude from Mauritania east through Niger, but south of normal over
Chad and Sudan. The result has been a tendency for above-normal
temperatures, below normal humidity, and below-normal rainfall in the
northern crop areas of Chad and Sudan.
Within this vein, the seasonal rains continued mostly favorable across
the Sahel, although there were some localities with too little rain and
some with too much. Weekly rainfall totals of 75 mm and higher in
western Senegal, northwest Burkina Faso, and southwestern Niger were
locally excessive, while below-normal rains persisted in Senegal's
eastern groundnut basin (weekly rainfall under 10 mm) and in the Lake
Chad area (under 15 mm). The latter area included west-central Chad,
extreme northern Cameroon, and extreme northeastern Nigeria. A
westward-tracking thunderstorm complex improved soil moisture on June
16-17 in Niger's central and eastern crop areas. Locally heavy rains
reaching 100 mm threatened flooding in central and southeastern
Nigeria. Farther west, the midsummer dry period remained intact along
the Gulf of Guinea coast, despite spotty heavy rains in southern parts
of Togo and Benin. In Sudan, the seasonal rains progressed northward,
bringing beneficial moisture to Sahelian crop zones. However, estimated
rainfall totals (2-20 mm) remained below normal in west-central Sudan,
particularly in Darfur province. Rains may have been locally excessive
(exceeding 100 mm) from western Eritrea southward into northwestern
Ethiopia and westward into adjacent areas of Sudan, but the moisture may
have benefitted parts of Eritrea (Anseba, for example) that had earlier
been reported as too dry.
July 25, 2001
For the period July 11-20, the ITCZ advanced about 0.8 degrees north of
its position during the previous period. There was still a southward
bias from western Chad through eastern Sudan, where the convergence zone
was located around 15.3 degrees north, compared to a twelve year mean
position of 16.0 degrees north. Though a southward discrepancy exists,
it is to a much lesser extent than earlier in the season, when monsoonal
rains were much weaker in the region. As is normal for the period, the
peak northward position of the ITCZ is occurring around 7.5 degrees west
longitude. Partially due to this northward position, seasonal rains have
begun to diminish along coastal areas of the Gulf of Guinea.
The northward shift of the ITCZ brought important rainfall to northern
Senegal, central Mali, central Niger, central Chad, central Sudan and
northern Ethiopia. During the past week, beneficial rains fell in areas
that had been trending dry, including the Lake Chad area, east-central
Chad and west-central Sudan, and parts of Senegal's groundnut basin.
The mid-season dry period remained entrenched over Liberia, southern and
central Cote d'Ivoire and southern Ghana, while slight rains persisted
over southern Togo, Benin and southwestern Nigeria. Unseasonably heavy
rain fell over Uganda and surrounding regions and also over the
southwestern coast of South Africa.
August 1, 2001
One of the elements we continue to monitor is the sea surface
temperature in the Pacific Ocean. Attached (fcstsst.gif) for your
information is the latest sea surface temperature forecast, by season,
produced by the NCEP, Climate Modeling Branch. We see that the lingering
cold surface water in the eastern Pacific is forecast to dissipate by
late 2001 and be replaced by relatively warm water by early 2002. We
will continue to monitor the timing and magnitude of the warming as it
represents possible impacts on the precipitation and temperature over
Africa.
Rainfall remained generally favorable in the Sahel countries. Weekly
rainfall totaled 25 to 50 mm from eastern Senegal to Chad, with locally
excessive amounts of 75 mm or more in parts of Mali and southern Chad.
Amounts were lighter in central Sudan, west-central Chad, southeastern
Niger, Gambia and Senegal's groundnut basin, but these areas saw
beneficial rains in the prior week. To the south, rainfall totaled only
0 to 10 mm in Liberia, southern Cote d'Ivoire, and southern Ghana.
Parts of southern Cote d'Ivoire and southern Liberia have seen little
rain in the past 3 weeks. In contrast, rains exceeded 75 mm for the
second week in northeastern Nigeria and extreme northern Cameroon.
Satellite-estimated amounts reached 200 mm locally along Nigeria's
southeastern border with Cameroon.
August 8, 2001
Continuing our discussion of the sea surface temperatures from last
week, over the past two years there has been a gradual expansion of the
area of positive equatorial subsurface temperature anomalies into the
central Pacific and a gradual decrease in the strength and areal extent
of the negative subsurface temperature anomalies in the eastern Pacific.
This evolution is consistent with the decay of the subsurface thermal
structure that characterizes the mature phase of cold episodes and the
development of conditions usually found just prior to warm episodes.
Accompanying this evolution has been a gradual transition from negative
to positive SST anomalies between 160°E and 130°W.
Positive SST anomalies are likely to continue in the equatorial Pacific
during the remainder of 2001 and into the first half of 2002. This
assessment is consistent with most coupled model and statistical model
predictions that indicate warmer than normal oceanic conditions through
early 2002. The impacts that this warming will have on global
temperature and precipitation patterns depend to a large degree on its
intensity. At the moment, there is considerable spread in the predicted
SST anomalies, with most predictions indicating a weak or moderate warm
episode (El Nino) by the end of 2001 and the beginning of 2002
Weekly updates for SST, 850-hPa wind, OLR and the equatorial subsurface
temperature structure are available on the Climate Prediction Center
homepage at: http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for
the evolution of El Nino/La Nina are updated monthly in CPC's Climate
Diagnostics Bulletin Forecast Forum. This ENSO Diagnostic Discussion,
which replaces the ENSO Advisories, will appear regularly around the
10th of each month on the CPC web site.
Rainfall remained mostly favorable across the Sahel, with weekly amounts
mainly in the 25 to 75 mm range. Less rain fell in the west. Although
increased rains benefitted Gambia and Senegal's southern groundnut
basin, amounts were below normal (1-10 mm) in eastern and northern
Senegal, including the northern groundnut basin. Rainfall has been
consistently below normal in this area during the current growing
season. To the south, dryness persisted in Liberia and central and
southern parts of Cote d'Ivoire and Ghana, with little or no rainfall.
Amounts were also low in southern parts of Benin and Togo. A break in
the rains is expected during this time of the year in the Gulf of Guinea
countries, but rainfall amounts have been less than usual, especially
from southern Liberia eastward to southwestern Ghana. Locally heavy
rains exceeding 75 mm fell in east-central Chad and adjacent Sudan, as
well as western Cameroon and southwestern Sudan and northwest Ethiopia.
In contrast, rainfall amounts appeared to be light (1-10 mm) in
south-central Sudan.
August 15, 2001
During August 1-10, the African ITCZ resumed this years general pattern,
with the western region located north of the climatological mean, and
the eastern region located south of the mean. The western region of the
ITCZ (10 degrees west to 10 degrees east) was located on average at 20
degrees north, compared to the long-term mean position of 19.1 degrees .
The ten day movement from last period of almost one degree north
continued to influence diminishing rains along the Ivory Coast and
increasing rainfall in Sahelian western Africa. The eastern region of
the ITCZ (from 20-35 degrees east) did not see this trend in average
movement, but actually moved about a half degree south of its position
last period. Although this southward bias did not appear to affect
rainfall in the region, this may be a hint that the ITCZ has reached its
maximum northward position earlier than the 1988-2000 climatological
figures indicate.
Rainfall has increased, generally, over much of the Sahel countries
compared to the previous 10 day period. Pockets of short-term dryness
over Burkina Faso and central Senegal received moderate showers during
the last days of this period. Examination of the meteorological
circulation shows a trough along Morocco maintaining the western branch
of the ITCZ to a higher position (23 degrees north). This extends
precipitation over northern Mauritania and Mali. Mid-season dryness
persisted over southern Liberia, southern and central Cote d'Ivoire,
most of Ghana, southern Togo and Benin, southwestern Nigeria and
southern Cameroon.
August 22, 2001
CCA Guidance for Sahel Rainfall in Aug-Oct 2001 at One Month Lead
With the sea surface temperature anomalies across the central equatorial
Pacific increasing over the past several months the CCA forecast for
the Sahel has been updated for the period August-October 2001. The
Sahel, defined here as the region between 10-25°N and 18°W-45°E,
receives the bulk of its annual mean rainfall during the northern
hemisphere summer when the ITCZ reaches its northernmost position. The
prediction for Aug-Oct 2001 Sahel rainfall at one month lead calls for
slightly higher than climatological probabilities for below normal
rainfall across much of western and central Sahel from Senegal to
western Niger. Slightly higher than climatological probabilities for
above normal rainfall are predicted over parts of northern and central
Ethiopia. Climatology is suggested elsewhere.
Tropical waves continued to bring ample rainfall from western Ethiopia
to Mali, but they tended to weaken or dive southward approaching
Senegal. As a result, unusually warm, dry weather prevailed across
Mauritania and northern and central Senegal during the past week.
Senegal's northern and western groundnut basin measured under 10 mm of
rain, with some locations in both Senegal and Mauritania reporting no
rainfall from August 8 to 20. As this is near the critical stage of the
crop season, rainfall will be very important in coming days and we will
continue to monitor the situation. Rainfall amounts were higher (25-50
mm), although still below normal, from western Gambia and southern
Senegal southward through Sierra Leone. Locally excessive rains
exceeding 100 mm fell in Burkina Faso. Dry weather again prevailed from
Liberia eastward through central and southern parts of Cote d'Ivoire and
Ghana and into southern parts of Togo, Benin, and Nigeria. The
mid-season dry period has been slightly drier than normal this summer in
the Gulf of Guinea countries.
August 29, 2001
During August 11-20, 2001, the West African portion of the ITCZ
retreated a small distance southward to 19.6 degrees N, which was north
of the long-term mean of 19.3 N and 0.4 degrees south of its previous
position (August 1-10, 2001). Overall progress so far this season has
been fairly typical, except for a spike northward during August 1-10.
The western ITCZ would have been near the 20th parallel again this
period if not for strong northerly winds in the west during August 18-20
driving the humid air southward across Mauritania. In the east, the ITCZ
jumped to its most northward position of the season, averaging 17.8 N
from 20 to 35 degrees E longitude. This was 0.5 degrees north of the
1988-2000 mean and a significant advance of 1.4 degrees from the
previous position.
Tropical waves again brought abundant rainfall to the Sahel countries
and eastward through Sudan. Weekly (August 21-27) rainfall totals
ranging from 10 to 25 mm improved moisture conditions in northern
Senegal, although rainfall deficits remained. Another 20 to 60 mm fell
in Senegal's groundnut basin on August 28, but less fell to the north,
where 4-week rainfall accumulations remained well under 50% of normal.
Totals of 10 to 50 mm also boosted conditions in Mauritania. Excessive
rains, with amounts exceeding 75 mm, fell in southern Burkina Faso,
northern parts of Ghana, Togo, Benin, and Nigeria, southern Chad, parts
of the Central African Republic (CAR), southwestern and eastern Sudan,
and northwestern Ethiopia. Weekly totals exceeded 100 mm in parts of
southern Chad and western CAR. Two of the last 3 weeks have been
abnormally wet in southern Chad. In east-central Sudan's Nile basin,
this was the second week that saw locally heavy rains, resulting in
increased flood threat. Although heavy showers fell in northwest
Ethiopia, estimated amounts were light in south-central areas, totaling
under 10 mm south of Addis. Long-term drought persisted over
southeastern Ethiopia, the pastoral areas of Kenya, and much of
Somalia. Rainfall increased over the southern and central Gulf of
Guinea countries, although little rain fell along the coast from
southern Liberia to southern Nigeria. Heavy rains eased dryness in
central Cote d'Ivoire on the 28th.
September 6, 2001
With the West African portion of the ITCZ at about its most northernmost
position, the easterly waves coming off the coast pose the potential for
hurricane development in the Atlantic Ocean. The Climate Prediction
Center forecast for this hurricane season is:
Expected Level of Overall Activity - Normal
Our forecast is for a 50% chance of normal levels of activity during the
2001 Atlantic hurricane season, a 25% chance of above-normal activity
and a 25% chance of below-normal activity.
The active tropical waves across the Sahel countries resulted in
scattered areas again recording heavy rainfall amounts. Totals exceeded
75 mm for the week ending August 3 in east-central and west-central
Chad, southern Nigeria and adjacent southern Cameroon, isolated
locations in northern Nigeria, southern and southeastern Burkina Faso,
and southern and central Mali. Lighter amounts falling over southern
Chad, northern Nigeria and eastern Sudan reduced the flood threat in
these countries. The moisture further reduced dryness over Senegal's
groundnut basin, although rainfall deficits remained in parts of
Senegal, especially in the north. A large complex of thunderstorms
crossed Mali and Senegal during August 4-5. In Ethiopia, satellite
estimates suggest below-normal rainfall in the west to the south of Lake
Tana during the past 4 weeks and over central areas during the past 3
weeks. Heavy rainfall diminished in northwest Ethiopia. Rainfall
remained light along the Gulf of Guinea coast from southern Liberia to
southwestern Nigeria. Increased rainfall inland suggested the
mid-summer dry period will soon end. In southern Africa, abnormally
heavy rains extended from the Free State southward through Lesotho to
the coast, with the possibility of heavy snow in Lesotho's mountains. A
second week of heavy showers hit the Cape Town area, where flooding has
been reported.
September 13, 2001
During the period from September 1-10, the African ITCZ maintained
similar spatial characteristics from the pervious period, but continued
a general southward movement. The average position of the western ITCZ
region (from 10 degrees west to 10 degrees east longitude) is just south
of its location during the final ten days of August. This position is
reflected by the continued lack of rainfall in areas of Liberia and Cote
D'Ivoire, with heavier rains extending from Senegal through northern
Nigeria. The current eastern ITCZ position, averaged from 20-35 degrees
east longitude remains with a southward bias from the climatologically
mean position on the order of one degree. The peak northward position
did occur in mid-August. This feature is reflected in the cumulative
satellite estimated rainfall map for the same period, with a lack of
precipitation in areas of central Sudan. Overall, the average position
of the African ITCZ is similar to the 1988-2000 mean, but a discrepancy
does exist in eastern regions.
Associated with the ITCZ, tropical waves continued to track westward
across the Sahel countries, bringing additional heavy rains to scattered
areas. Reflecting the usual seasonal shift in the weather pattern, the
rainfall band retreated southward across the central and eastern Sahel
region, and amounts were not quite as heavy as in preceding weeks.
Totals of 50 to 75 mm during September 4-10 threatened additional or
continued flooding in eastern Sudan, northwestern Ethiopia, southern
Chad, northern Nigeria, southwestern Cameroon, southern Mali, and
central Senegal. Excessive rains exceeding 75 mm also hit Uganda to the
north of Lake Victoria. Increased rains fell over southwestern
Ethiopia, which had been abnormally dry in early to mid-August,
according to satellite estimates, but rainfall remained light in central
Ethiopia, continuing a dry trend that began in late July. Estimated
amounts also remained light in the eastern Darfur region of west-central
Sudan, where satellite vegetation imagery implies below-average
conditions and the ITCZ has been persistently south of normal.
Beneficial drier weather prevailed across South Africa.
September 20, 2001
Although most oceanic and atmospheric indices reflect ENSO-neutral
conditions, there are indications that a warm episode will develop
during the remainder of 2001. Over the past two years there has been a
gradual eastward shift of the area of positive equatorial subsurface
temperature anomalies from the western equatorial Pacific into the
central equatorial Pacific. This evolution is consistent with the decay
of the subsurface thermal structure that characterizes the mature phase
of cold episodes and the development of conditions usually found just
prior to warm (El Nino) episodes. Accompanying this evolution has been a
gradual transition from negative to positive SST anomalies and a gradual
return to near normal low-level winds in the central equatorial
Pacific.
There is no clear consensus amongst the latest statistical and coupled
model predictions. However, several of these predictions indicate that
positive SST anomalies will continue in the central equatorial Pacific
during the remainder of 2001 and into the first half of 2002. The
impacts that this warming will have on global temperature and
precipitation patterns depend to a large degree on its intensity. At the
moment, considering both the SST predictions and the observed oceanic
and atmospheric circulation patterns, it seems most likely that the
intensity of the warming will be weak or moderate.
Weekly updates for SST and other features of the equatorial thermal
structure are available on the Climate Prediction Center homepage at:
http://www.cpc.ncep.noaa.gov.
Unseasonably heavy rains struck Lesotho and southeastern South
Africa in the Kwazulu-Natal area on September 11-13, with totals ranging
from 75 to 150 mm. This compares with normal weekly totals in the 5 to
10 mm range. Another storm system dropped heavy rains on Northern and
Eastern Cape Provinces and western Free State during September 18, with
reported 24-hour amounts up to 65 mm. This contrasts sharply with
normal weekly totals of 1 to 3 mm. Isolated heavy showers also hit
Angola, Namibia, and southern Mozambique during the week. To the
north, the seasonal rains continued their typical southward migration,
as rainfall tapered off in parts of the Sahel and increased along the
Guinea Gulf. Estimated rainfall amounts during the week ending
September 17 reached 100 to 200 mm in southeastern Nigeria. Moderate
rains of 10 to 50 mm eased dryness in southern parts of Liberia, Cote
d'Ivoire, Ghana, Togo, and Benin. Excessive totals of 75 mm or more hit
parts of southwestern Sudan and southern Chad, as well as much of the
Central African Republic. Rains eased dryness in the southern parts of
Sudan's Darfur province, but totals remained light in the northern crop
areas of eastern Darfur.
September 27, 2001
During September 11-20, 2001, the West African portion of the ITCZ
retreated 1.2 degrees latitude southward to 17.5 degrees N, which is
near the long-term mean. Overall progress this season favored ample and
timely rainfall for the Sahel countries. In the east, the ITCZ's
average position of 15.2 N was near last period's location (15.1 N) and
0.5 degrees south of its 1988-2000 mean. The ITCZ was near its normal
latitude over Mauritania and Mali, but south of normal from Niger to
western Sudan.
Heavy rains diminished in central South Africa after September 19 while
favorably dry weather prevailed over previously-wet areas in
southeastern South Africa and Cape Town in the west. To the north,
locally heavy rains exceeding 75 mm in the past week fell over southern
Chad, western Nigeria, and southwestern Cameroon. Rainfall totals
exceeded 100 mm in western Kenya near Lake Victoria, but long-term
drought continued over northern and eastern Kenya, Somalia, and
southeastern Ethiopia.
October 4, 2001
During the period from September 21-30, 2001, the western region of the
African ITCZ retreated 0.9 degrees southward from its previous position
while the eastern ITCZ region retreated approximately 0.7 degrees
southward. For most of the season the western region has been very close
to its normal position while the eastern region has been generally
located south of normal. The latest dekadal satellite-estimated rainfall
map indicates a correspondence between rainfall location and ITCZ
position, as rains have increased southward into the coastal Gulf of
Guinea and central African locations.
Heavy rains (75-150 mm in the past week) persisted in northwest Nigeria
and expanded across southeast Nigeria and Cameroon's border area.
Locally heavy rains exceeding 75 mm also hit Cote d'Ivoire, Ghana, Togo,
and Benin. Conditions likely remain too wet in parts of the southern
half of Sudan, with another 25 to 50 mm of rain and locally heavier
amounts. Little or no rain fell across the long-term drought areas of
southern and southeastern Ethiopia and northern and eastern Kenya, as
well as southern Somalia. Scattered showers did fall over central and
northern Somalia, likely signaling the start of the minor rainy season
there. The minor season rains should start soon elsewhere across the
African Horn, as the season typically begins by early October.
Satellite imagery shows an increase in mid-level moisture, suggesting
rainfall will increase shortly. The season has started late along the
southeast coast of Kenya and the northeast coast of Tanzania, where
normal weekly rainfall is 15-20 mm and amounts varied from 0 to 4 mm.
October 11, 2001
As there have been several tropical depressions already observed in the
South Indian Ocean, we include within this preamble the current sea
surface temperature information for this region. Within sst.gif we see
that the South Indian Ocean for the period September 30 - October 6 is
generally about 0.5-1.5 degrees above the 1961-1990 average with
slightly warmer temperatures between Indonesia and Australia. In
general, these warmer sea surface temperatures are more conducive to
enhanced cyclone activity due to greater availability of tropical
energy. These sea surface temperature products are updated weekly by
the NCEP/Environmental Modeling Center and are found at the web site:
www.emc.ncep.noaa.gov/research/cmb/sst_analysis
We will continue to monitor the sea surface temperatures and the cyclone
development throughout the season.
Satellite estimates indicated heavy rainfall amounts of 75 to 200 mm
during the week ending on October 8 in extreme southern Sudan (Eastern
Equatoria Province). This is more rain than is normally experienced
during the entire month of October. In contrast, dry weather dominated
the African Horn, with only widely scattered showers over Somalia,
southern Ethiopia, the pastoral areas of Kenya, and most of Tanzania.
Rainfall has been abnormally light since September in southeast coastal
Kenya and northeast coastal Tanzania. More recently, the onset of the
minor season rains has been somewhat late in Somalia, southern Ethiopia,
Kenya's pastoral areas, and northern Tanzania. Much of this region is
already affected by a long-term drought.
October 18, 2001
Most oceanic and atmospheric indices reflect ENSO-neutral conditions.
However, there are
indications that a warm episode may develop during the next several
months. Since late June 2001 sea surface temperatures (SSTs) have become
anomalously warm in the central equatorial Pacific, with anomalies near
1°C in the vicinity of the date line. During the same period, subsurface
temperature anomalies have remained positive in the central equatorial
Pacific between 170°E and 120°W, indicating a deeper than normal
thermocline in that region. This pattern has been observed during the
early stages of past warm episodes.
In recent months, many tropical Pacific atmospheric and oceanic
variables have been modulated by intraseasonal (30-60 day) activity. In
the past, such activity has been instrumental in producing low-level
wind fluctuations during both the onset and demise phases of warm
episodes. Since we are currently in a transition season, special
attention will be focused on the evolution of this activity and any
effect that it has on surface and subsurface ocean temperatures.
There is no clear consensus amongst the latest statistical and coupled
model predictions. However, several of these predictions indicate that
positive SST anomalies will continue in the central equatorial Pacific
during the remainder of 2001 and into the first half of 2002. The
impacts that this warming will have on global temperature and
precipitation patterns depend to a large degree on its intensity. At the
moment, considering both the SST predictions, the time of year and the
observed oceanic and atmospheric circulation patterns, it seems most
likely that the intensity of any warming will be weak or moderate.
In East Africa, the minor season rains continued below normal, with
weekly totals during October 9-15 of 0 to 10 mm over extreme southern
Ethiopia, southern Somalia, the pastoral areas of Kenya, and northern
Tanzania. Four-week rainfall has totaled less than 25% of normal along
the coast of Kenya and at scattered locations in the interior. Areas of
southern Ethiopia farther north did measure up to 10 mm of rain, easing
short-term dryness. Farther west, rainfall amounts diminished from the
excessive levels recorded during the previous week in southern Sudan and
northern Uganda. In southern Chad, a large thunderstorm complex brought
heavy rains on October 16, threatening renewed flooding.
October 25, 2001
During the period from October 11-20, 2001, the African ITCZ continued
moving southward at a slightly faster than normal pace. The western
region (10° west to 10° east) was located on average 1.1° south from the
previous period, and 0.9° south of its climatological normal position
southward bias remains for the eastern region of the ITCZ from 20-35°
east, a pattern that has virtually existed for this entire season.
A look at the 10-day satellite estimated rainfall map shows
precipitation prominent throughout the CAR, and some amounts exceeding
50 mm for the period in northern Angola. This pattern coincides well
with the southward movement of the ITCZ. Light rains prevailed across
much of the Greater Horn of Africa, signaling a slow start of the short
rainy season. The exception was central and western Ethiopia, where
favorable rains were observed. Consistent with the southward retreat of
the ITCZ, heavy downpours soaked central and southeastern Nigeria.
Although rains remained steady throughout most of southern Uganda, a
lack of precipitation occurred along coastal areas of Kenya and southern
Somalia, where five week rainfall totals are less than 20% of normal.
As opposed to late September/early October, rainfall was generally light
over northern Algeria and Morocco as drier air pushed through the
region, while temperatures averaged 2-7 degrees warmer than normal.
Lighter rains continued over parts of eastern Guinea and southern Chad,
but totals moderated to generally less than 40 mm, as opposed to more
excessive amounts that fell in September. Heavy rains soaked areas of
coastal Cote d'Ivoire, Ghana, central Gabon, and southern Congo, with
totals exceeding 100 mm locally. These rains in the Gabon region helped
to ease the dryness that has been affecting the area, but short term
dryness still remains further south into northern Angola. In southern
Africa, unseasonable moderate rains fell over Zimbabwe. Moderate to
heavy rains were also observed over
northeastern South Africa. Elsewhere, locally moderate rains were
observed over central and
western Zambia, northeastern and northwestern Mozambique, northern and
southeastern Madagascar.
October 31, 2001
The first named cyclone (Alex/Andre) of this season in the South Indian
Ocean has occurred and we note that in early October we included a
discussion of the observed sea surface temperature information for this
region. For this preamble we update this information and within sst.gif
we see that the South Indian Ocean for the period October 21-27 remains
about 0.5-1.5 degrees above the 1961-1990 average with slightly warmer
temperatures in the vicinity of Indonesia. In general, these warmer sea
surface temperatures are more conducive to enhanced cyclone activity due
to greater availability of tropical energy. These sea surface
temperature products are updated weekly by the NCEP/Environmental
Modeling Center and are found at the web site:
http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis.
In East Africa, showers (10-75 mm) covered southern and southeastern
areas of Ethiopia as well as much of Somalia during the past week,
easing short and long-term dryness. The minor rainy season appears to
be established over both countries following a somewhat slow start.
However, abnormally dry conditions continued over southern Somalia, the
pastoral areas of Kenya, and northern and eastern Tanzania, as rainfall
totals for the week ending October 30 were negligible. Four-week
rainfall has totaled under 25% of normal in central and eastern Kenya,
and similar deficits are likely in adjacent southern Somalia and across
northern and eastern Tanzania. The recent dryness has aggravated
long-term drought over Kenya and southern Somalia. Farther south, heavy
rains hit central South Africa, with weekly totals of 75 to 100 mm in
the southern part of the maize triangle and up to 200 mm near the coast
south of Lesotho.
November 7, 2001
During October 21-31, 2001, the ITCZ continued its rapid retreat
southward. The West African portion of the ITCZ (10 degrees W to 10
degrees E) dropped 2.1 degrees latitude south to 11.4 degrees N, which
was 1.3 degrees south of the long-term mean. This was the farthest
south for October 21-31 since 1989 (11.2 N). In the east (20 to 35
degrees E), the ITCZ's average position of 10.3 N was 1.2 degrees south
of last period's location and 1.1 degrees south of its 1988-2000 mean.
The ITCZ was located well south of normal over much of its length, with
only the far western end over Senegal and the far eastern end over Sudan
near the
long-term mean location. Consistent with this pattern, plentiful rains
fell over western
Ethiopia and extreme eastern Sudan, but dry conditions held sway across
the rest of the region south to about the 6th parallel from around 25 E
to 10 W. This is the last ITCZ update for the year. Resumption of
ITCZ monitoring is planned to resume next April.
The first named cyclone (Alex/Andre) of this season in the South Indian
Ocean dissipated over the mid-Indian Ocean and ceased to be of cyclone
strength. The remnants have continued to move westward. It appears the
storm system will move just north of Madagascar and will not pose a
significant threat to the continent.
In East Africa, heavy showers ended dryness across parts of Kenya, with
localized totals for the week ending on November 5 reaching 200 mm in
southeastern interior areas. Nevertheless, long-term drought persisted
across northern Kenya, and pockets of short-term dryness also continued,
as weekly totals stayed under 10 mm in some locations. Abnormal dryness
also continued over the southern coast of Kenya and across much of
northeastern Tanzania. Many stations in the latter area have reported
4-week rainfall totals under 25% of normal. To the north, abnormally
wet conditions persisted from Uganda northward to southern Sudan, with
estimated amounts exceeding 50 mm in a number of areas, and totals
locally reaching over 100 mm in southern Sudan's western Equatoria
province. To the south, the summer rains have been slow to start over
Mozambique, northern and eastern Zimbabwe, and southern Malawi.
Rainfall has been negligible in recent weeks over much of this region.
November 14, 2001
Guidance for Southern Africa Rainfall in Dec-Mar 2001-2002 at One Month
Lead
Southern Africa is defined here as the region between 10°-35°S;
10-50°E. The prediction for Dec-Jan-Feb 2001-2002 southern Africa
rainfall at one month lead (Wassila.gif) is weak and calls for
climatology across much of southern Africa. Slightly higher than
climatological probabilities for above normal rainfall are predicted for
northeastern southern Africa, including northern Mozambique, Malawi, and
southern Tanzania.
In this forecast, quasi-global SSTs between 40°S and 60°N at a
resolution of 10° by 10° lat-lon are used to predict southern Africa
rainfall. The predictions are expressed in terms of departures from
climatological probabilities for the two extreme categories above and
below-normal rainfall. The climatological probability of each of these
categories is 0.33. The probability for the normal category remains
fixed at 0.33 because the statistical method has virtually no skill in
predicting this category. When skill is low, climatology is suggested.
Thus, no forecast is made. The diagnostic data indicate that Dec-Feb
Southern African rainfall has a modest predictability at 1 month lead.
Generous rains spelled some additional relief for eastern and coastal
areas of Kenya and southern Somalia. Rainfall intensified over central
and northern DRC. Wet conditions persisted over Lesotho and the
southeastern coast of South Africa. The rainfall situation improved over
Mozambique, Zimbabwe, Malawi and Zambia compared to the last ten days.
In southern Africa, satellite rainfall estimates indicated moderate
rains over northern and western Zambia, southern Zimbabwe, central and
northeastern Angola, most of Botswana, western Madagascar and pockets in
Mozambique.
November 21, 2001
Most oceanic and atmospheric indices reflect ENSO-neutral conditions.
However, there are indications of a slow evolution towards a warm
episode. Since late June 2001 sea surface temperatures (SSTs) have
become anomalously warm in the central equatorial Pacific, with
anomalies near 1°C just to the west of the date line. During the same
period, subsurface temperature anomalies have remained positive in the
central equatorial Pacific between 160°E and 120°W, indicating a
deeper-than-normal thermocline in that region. This pattern has been
observed immediately prior to the onset of past warm episodes.
The latest statistical and coupled model predictions indicate either
weak warm or near-normal conditions in the equatorial Pacific during the
remainder of 2001 and into the first half of 2002. However, all of these
prediction techniques have difficulty in making skillful forecasts
during ENSO transitions. Considering the SST predictions, the time of
year, and the observed oceanic and atmospheric circulation patterns, it
seems most likely that a gradual evolution to warm episode conditions
will continue in the tropical Pacific over the next several months.
For the weather features this week, we point out the continued
substantial rainfall occurring in southern Africa. As noted last week,
the prediction for Dec-Jan-Feb 2001-2002 southern Africa rainfall at one
month lead calls for climatology across much of southern Africa with
slightly higher than climatological probabilities for above normal
rainfall predicted for northeastern southern Africa, including northern
Mozambique, Malawi, and southern Tanzania.
November 28, 2001
With the formation of several tropical cyclone systems in the South
Indian, for this preamble we update the observed sea surface temperature
as this is a major factor in cyclone development. Within sst.gif we see
that the South Indian Ocean for the period November 18-24 has cooled
somewhat from earlier in the season and the temperatures are generally
near neutral with some areas remaining about 0.5-1.5 degrees above the
1961-1990 average. These sea surface temperature products are updated
weekly by the NCEP/Environmental Modeling Center and are found at the
web site:
http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/images/oisst.gif
For the weather features this week, we point out the continued
substantial rainfall occurring in the band from Zaire, Congo and Gabon
southeastward toward mid-southern Mozambique and northern South Africa.
December 6, 2001
We note that last year the first named cyclone in the South Indian Ocean
did not occur until early January whereas this year we have already had
two named cyclones. As was stated last week, the
sea surface temperatures in the Indian Ocean are generally near neutral
with some areas remaining about 0.5-1.5 degrees above the 1961-1990
average. We continue to monitor the situation and will appraise people
of possible landfall.
Moderate to heavy rains continued in pockets of eastern Kenya and
southern Somalia, while dryness continued to prevail over much of
Tanzania. Wet conditions remained across much of southern Africa, with
the heaviest rains located in Angola, Botswana, and southern Mozambique.
Dryness, however, continued over northern Mozambique. In central
Africa, Gabon, Congo, and DRC recorded heaviest amounts of
precipitation.
EDITORIAL NOTE: During this first year of producing the Africa Threats
Assessment we have had a continuing internal discussion concerning the
issuance of "threat" notices in areas that are receiving heavy rains
that are "near-normal". The concern is that we should focus on
perceived "true" threats and not overemphasize a position where a
routine statement can be made. For example, we have discontinued the
threat of heavy rain over Madagascar this week though the rains appear
likely to continue. You are the users of the product and we offer you
the opportunity to weigh-in on the issue. If you have any thoughts or
concerns please send them to Alvin.Miller@noaa.gov
December 13, 2001
At this start of the cyclone season in the South Indian Ocean, we have
added information to the CPC USAID/FEWS web site to aid your
understanding of the current cyclone situation. Under the URL
http://www.cpc.ncep.noaa.gov/products/fews/ there exists an additional
category of Cyclone Monitoring; Indian Ocean. It consists of a 24-hour
false-color infrared imagery loop of the Indian Ocean, a map of the 700
mb winds, and a current cyclone track image from the University of
Hawaii. Concerning the latter, we are investigating ways to implement
our own position graphic with forecast positions included.
Satellite imagery depicted a large thunderstorm complex over southern
Mozambique and adjacent parts of South Africa, Zimbabwe, and Swaziland
on December 11. This moisture comes on top of ground already wet from
persistent above-normal rainfall since October. Four-week rainfall has
totaled more than 200 percent of normal across much of southern Africa,
including Botswana, southern Zimbabwe, central and eastern South Africa,
and extreme southern Mozambique. Rainfall totals for the week ending
December 10 ranged from 30 to 100 mm in a band stretching from southern
Mozambique northwestward through Zimbabwe, Zambia, Angola, into DRC. To
the northeast, the area that has seen persistent dryness since October,
including eastern Tanzania and northern Mozambique, measured 5 to 30 mm
in the past week. This is not enough rainfall to significantly relieve
dryness, but the increased shower activity may be a sign that the rainy
season is finally beginning.
December 20, 2001
Heavy showers on December 10-11 contributed to flooding in northeastern
South Africa and southern Mozambique, but rainfall has since diminished
in both areas as the axis of heaviest rains has shifted northward.
Heavy showers have moved into the dry areas of northern Mozambique, but
amounts remained relatively light (1-25 mm) over extreme northern
Mozambique this past week. Overall conditions remained abnormally wet
from Zambia southward to South Africa and eastward through southern
Mozambique, with many stations recording over twice their normal
rainfall totals in the past 4 weeks. Showers (1-25 mm) eased drought
over eastern Tanzania, but much more rain is needed to make an
appreciable dent in the deficits that have been accumulating since
October. Showers also eased dryness in eastern and northern Kenya,
where long-term drought persisted in the north.
On a more positive note, the sea surface temperatures in the eastern
portion of the South Indian Ocean have cooled considerably over the past
several weeks. This has been accompanied by a lack of cyclone
development in the area.
December 27, 2001
Most oceanic and atmospheric indices reflect a continuation of
ENSO-neutral conditions. However, there are indications of a slow
evolution towards a warm episode. Since late June 2001 sea surface
temperatures (SSTs) have become anomalously warm in the central
equatorial Pacific, with anomalies near 1 Degree C just to the west of
the dateline. During the same period, subsurface temperature anomalies
have remained positive in the central equatorial Pacific between 160E
and 120W indicating a deeper-than-normal thermocline in that region.
Similar patterns have been observed immediately prior to the onset of
previous warm episodes.
The majority of the latest statistical and coupled model predictions
indicate near-normal conditions in the equatorial Pacific during the
next three to six months. However, all of these prediction techniques
have difficulty in making skillful forecasts during ENSO transitions.
Considering the time of year, and the observed oceanic and atmospheric
circulation patterns, it seems most likely that a gradual evolution to
warm episode conditions will continue in the tropical Pacific over the
next several months.
Heavy rains moved northward into central and northern Mozambique during
the period from December 18-24, as precipitation totals exceeded 100 mm
locally with widespread amounts greater than 50 mm throughout the
region. Although southern Mozambique dried out somewhat, coastal areas
of southeastern South Africa received rains totaling 100 mm, while
further inland amounts were generally less than 50 mm. The heaviest
showers in central Africa were confined to central DRC where scattered
satellite estimated rainfall totals topped the 100 mm mark. As opposed
to previous months, the region surrounding Gabon accumulated much less
rainfall during the past week, with totals generally less than 25 mm,
except in northern Congo where rains exceeded 50 mm locally. Rains
diminished in coverage throughout southern Somalia and eastern Kenya,
although pockets of heavy rainfall were recorded east of Nairobi.
Precipitation throughout much of northern Morocco was the heaviest of
the season, with rainfall totals greater than 100 mm recorded. Although
some relief occurred in northern areas, most of the rain did not fall in
the central and southern dryness affected region of the country.
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